This invention relates to a combustion system which uses hydrogen perioxide as a propellant and more particularly to a combustion system which uses dilute solution of hydrogen peroxide and a fuel as a propellant.
Propulsion systems, and particularly those used in underwater applications, have used hydrogen peroxide as a propellant for many years. Although sometimes it is used as a monopropellant, it is often used as an oxygen source, i.e., an oxidizer, in combination with a fuel. In such a conventional system, concentrated hydrogen peroxide (H.sub.2 O.sub.2) is delivered into a decomposition chamber where it is catalytically decomposed to form oxygen (O.sub.2) gas and H.sub.2 O. This process being exothermic results in the generation of heat called "heat of decomposition". O.sub.2 and H.sub.2 O produced then proceed into a combustion chamber where oxygen is combined with a fuel in a stoichiometric ratio. This mixture is then ignited to produce hot gas under pressure which is delivered to a prime mover such as a turbine, piston or a rotary engine. The H.sub.2 O produced during decomposition serves to depress the final combustion temperature and becomes part of the working fluid delivered to the prime mover. The decomposition of high concentrations of H.sub.2 O.sub.2 results in the generation of O.sub.2 and H.sub.2 O as a satuated vapor. At lower concentrations (less than 67% or so), however, the quality of H.sub.2 O drops due to the lower heat of decomposition and liquid phase H.sub.2 O is present. Increasing the pressure in the system further increases the percentage of liquid H.sub.2 O present. As an example, decomposition of 40% concentration H.sub.2 O.sub.2 at 1400 PSI (pounds per square inch), results in the generation of oxygen (O.sub.2) gas and H.sub.2 O and H.sub.2 O so produced being completely in the liquid phase. When the liquid phase H.sub.2 O produced during the decomposition process enters the combustion chamber, it is vaporized and superheated to the equilibrium temperature of the overall combustion process. The heat required to vaporize and superheat the liquid H.sub.2 O is supplied by the energy resulting from the combustion of O.sub.2 and the fuel. This lowers the final temperature of the mixture being delivered to the prime mover and results in lower prime mover performance. It is thus desirable to remove the liquid phase H.sub.2 O produced during the decomposition before the combustion process and thus prevent reduction of performance of the prime mover by increasing the temperature of the hot gas, which in turn improves the overall performance of the prime mover despite the decrease in performance due to decrease, due to H.sub.2 O extraction, in the mass of hot gas delivered to the prime mover.